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james bunn
2,377 PointsClosure as a function parameter
In the video, Pasan mentioned the function getRecentBlogPosts has two closures.
First, the "completion" parameter of the function getRecentBlogPosts is a closure Next, the second parameter of the downloadTaskWithRequest method is a closure.
I understand how the second parameter of the downloadTaskWithRequest method is a closure because it follows the syntax mentioned in the prior videos. However, I don't understand how (completion: NSURLResponse! -> Void)) is a closure.
func getRecentBlogPosts (completion: (NSURLResponse! -> Void))
{
let treehouseDownloadTask = session.downloadTaskWithRequest(request)
{ (let url, let response, let eror) in }
2 Answers
Andrew Taylor
11,500 PointsI am guessing from looking at the code NSURLRepsonse returns void if it is not passed anything (null) and is therefore a closure.
Andrew Taylor
11,500 PointsThe variable "completion" I guess is doing that. Although it is a parameter, it is essential a variable expect you will initialize it when you call the function.
james bunn
2,377 PointsRight, so what variable is "completion" variable capturing that is outside its original scope? I assume it's the "response" object. I just don't understand how the "response" object is outside the original scope
james bunn
2,377 Pointsjames bunn
2,377 PointsI thought in order to be a closure, you have to capture variables which are outside the original scope. Which variables is "completion" capturing?